1. Field of the Invention
The present invention relates to a magnetic recording/reproducing apparatus, and in particular to a clutch device for a magnetic recording/reproducing apparatus which is capable of transmitting power for regularly conveying a tape, regardless of the quantity of the tape, wound around a reel.
2. Description of the Prior Art
FIG. 1 illustrates a tape path conveying structure of a general magnetic recording/reproducing apparatus.
As shown in FIG. 1, a supplying reel driving body 1 and a winding reel driving body 21 are installed to drive a supplying reel (not shown) and a winding reel (not shown) of a tape cassette (not shown) at one side of a main chassis (C).
A plurality of posts and guide rollers are provided on the main chassis (C) to guide the path of a tape (T) released from a tape cassette.
A tension post 3 for controlling the tensile force of the travelling tape (T) is installed on a tension arm 4.
The tension arm 4 is rotated at a predetermined angle according to the tension of the tape (T) on the main chassis (C) centering around a shaft pin 2, on which the tension arm 4 is elastically supported by a spring 5.
The tape (T) having passed the tension post 3 is guided by a guide post 6 and transmitted to a full width erasing head 7.
The full width erasing head 7 removes, in advance, a signal which has been recorded on the tape in a recording mode.
An inertia roller is installed at a position past the full width erasing head 7 to guide the path of the tape (T).
Next, the tape (T) is guided by guide posts 10 and 11 of the supplying and winding side which are moved along loading paths formed at both sides of a rotational head drum 9.
The guide posts 10 and 11 draw the tape (T) from the inside of the tape cassette, a position indicated by a dotted line as shown in FIG. 1, so as to be wound and traveled.
A supplying slant post 12 and a winding slant post 13 are provided next to the guide posts 10 and 11 and in the direction of the rotational head drum 9, so as to guide the conveyance of the tape (T).
The guide posts 10 and 11 and the slant posts 12 and 13 are installed on respective supplying and winding slant bases 14 and 15 and moved along the loading path.
As shown in FIG. 1, the rotational head drum 9, on which the tape (T) is wound and conveyed, is provided with a rotational head (not shown) for reading a signal recorded on the tape (T) or for recording a signal.
The tape (T) passes the rotational head drum 9 and the slant post 13 and the guide post 11 of the winding side and then passes the audio control head 16. The audio control head 16 deletes, records and reproduces an audio signal, and records and reproduces a control signal.
A guide post 17 is provided on the main chassis (C), adjacent to the audio control head 16 for controlling the traveling height of the tape (T).
A capstan shaft 18 for providing a traveling force to the tape (T) is installed at a position past the guide post 17. The capstan shaft 18 is an output shaft of a capstan motor (not shown) installed at the opposite face of the main chassis (C), and the traveling direction of the tape (T) is determined by the rotational direction of the capstan motor.
A pinch, roller 19 is selectively installed to tightly engage the capstan shaft 18 to provide a force for pulling the tape (T).
A winding post 20 is provided adjacent to the location of the pinch roller 19 and the capstan shaft 18. A winding arm (not shown) is installed and moved at the winding post 20.
Between the supplying reel driving body 1 and the winding reel driving body 21, a clutch assembly 22 is installed to drive the supply reel or the winding reel at a certain torque, regardless of the amount of tape (T) wound on the supplying reel or the winding reel, upon receipt of a driving force received from the capstan motor.
An idler gear 24 is installed at a front end of an idler arm 25 which is coaxially installed with the clutch assembly 22. The idler gear 24 is adopted to selectively engage either the supply reel driving body 1 or the winding reel driving body 21 for transferring a driving force thereto upon receipt of the driving force from the clutch assembly 22.
A tension brake 27 is wound on the supplying reel driving body 1 with both of its ends fixed to the tension arm 4. The tension brake 27 controls the rotational speed of the supplying reel driving body 1 according to the operation of the tension arm 4, thereby controlling the tension in the tape (T).
The construction of the clutch assembly 22 will be described in detail with reference to accompanying FIGS. 2 and 3.
As depicted in FIGS. 2 and 3, a central shaft 30 is installed on the main chassis C. A driving pulley 32d is installed so as to rotate centering around the central shaft 30. A belt 31 which receives power from the capstan motor is wound around the driving pulley 32d for transferring the rotational force of the capstan motor. A cylindrical clutch holder 34 is installed on the driving pulley 32.
A an up/down gear 36 is installed on the central shaft 30 on the same axis as the driving pulley 32d. The up/down gear 36 transmits the power from the capstan motor by selectively engaging the idler gear 24. Clutch springs 18, 18xe2x80x2 are installed to the up/down gear 36. The clutch springs 18, 18xe2x80x2 are wound around the outer circumferential surface of the cylindrical clutch holder 34. Herein, the lower spring 18 and the upper spring 18xe2x80x2 are wound in the opposite directions.
According to the rotational direction of the driving pulley 32d, for example, when the lower spring 18 is locked and the upper spring 18xe2x80x2 rubs against the surface of the clutch holder 34, a slip occurs. Accordingly, the movement of the tape (T) can be performed with a regular torque regardless of the quantity of the tape (T) wound around the reel.
In the meantime, a first gear portion 37 and a second gear portion 37xe2x80x2 are formed on the up/down gear 36, the first and the second gear portions 37, 37xe2x80x2 reducing and transmitting power by respectively and selectively engaging with gear portions of the idler gear 24.
The idler gear 24 is rotatably installed on the front end portion of the idler arm 25, centering around the central shaft 30, each gear portion (not shown) selectively engaging the first and the second gear portions 37, 37xe2x80x2 of the up/down gear 36. The idler gear 24 transmits the power of the capstan motor to the supplying reel and the winding reel by selectively engaging with the supply reel body 1 and the winding reel body 21.
However, the above-mentioned conventional magnetic recording/reproducing apparatus has the following problems.
The clutch springs 18, 18xe2x80x2 are selectively used for conveying the tape (T) with a regular tension, regardless of the quantity of tape (T) wound around the supply reel and the winding reel in accordance with a traveling direction of the tape (T).
In this use of clutch springs 18, 18xe2x80x2, production costs are increased due to the large amount of construction parts. In addition, the operation efficiency of the assembly process is reduced.
In order to solve above-mentioned problems, it is an object of the present invention to provide a clutch device for a magnetic recording/reproducing apparatus which is capable of reducing production cost and improving the efficiency of the assembly operation by minimizing the number of components.
In order to achieve the above-mentioned object, a clutch device for a magnetic recording/reproducing apparatus is provided which includes a rotating central shaft installed on a main chassis; a driving pulley installed on the rotating central shaft which rotates by receiving power from a driving source and having a cylindrical pulley holder portion; an up/down gear containing a cylindrical gear holder unit having an outer diameter smaller than an inner diameter of the pulley holder portion and being ascendable/descendable along a rotating central shaft; and a clutch spring placed between the inner surface of the pulley holder portion and the outer surface of the gear holder unit for selectively transmitting power with a certain torque from the driving pulley to the up/down gear in accordance with the rotational direction of the driving pulley.
The clutch spring has a coil spring structure, with the end of the clutch spring contacting the inner surface of the pulley holder portion, and the other end of the clutch spring contacting the outer surface of the gear holder unit.
Certain portions of the pulley holder portion and the gear holder unit are formed so as to project out toward the clutch spring in order to engage the clutch spring.
The gear holder unit includes an outer cylindrical portion having an inner diameter larger than an inner diameter of the pulley holder portion and connected to the pulley holder portion.
The driving pulley and the up/down gear respectively include an engaging means which enables them to mesh and rotate together when the up/down gear is transferred toward the driving pulley.
The driving pulley and the up/down gear respectively include a movement restriction means restricting the up/down gear from moving in a specific range when the up/down gear moves in a direction separated from the driving pulley.
The up/down gear is constructed with a gear unit having a large gear and a small gear and a gear holder unit, and the gear unit and the gear holder unit are combined with each other.
A boss portion is formed at the center of the gear unit, with the large gear being formed at a disc-shaped portion which extends from the boss portion. The small gear which has a diameter smaller than the diameter of the large gear is formed at the side of the disc-shaped portion.
A cylindrical holder supporting portion is formed at the other side of the gear unit so as to support the gear holder unit.
The gear holder unit is constructed with an inner cylindrical portion and an outer cylindrical portion, and the clutch spring contacts the inner cylindrical portion, and an engaging rib is formed at the outer cylindrical portion.
The inner cylindrical portion has a hook structure for engaging with the drive pulley.
The drive pulley of a clutch device for a magnetic recording/reproducing apparatus includes a pulley body formed as a disc shape with a belt wound around the outer circumference thereof; a boss portion combined with a rotating central shaft; a bridge portion projected so as to restrict the movement of an up/down gear; a pulley holder portion having an inner surface in contact with a clutch spring; and an engaging rib combined with an up/down gear for rotating together; wherein the boss portion, the bridging portion, the pulley holder portion and the engaging rib are formed in a cylindrical shape and orderly positioned from the center of the pulley body.
A clutch spring of a clutch device for a magnetic recording/reproducing apparatus includes an inner contacting portion for engaging an up/down gear and having a plurality of windings; an outer contacting portion for engaging a drive pulley and having a plurality of windings; and a connecting portion connecting the inner contacting portion and the outer contacting portion and containing a plurality of windings less than those of the inner contacting portion and the outer contacting portion.
The diameter of the inner contacting portion is formed to be smaller than the diameter of the outer contacting portion.
Accordingly, a clutch device for a magnetic recording/reproducing apparatus in accordance with the present invention is capable of reducing a production cost and improving the efficiency of an assembly operation by minimizing the number of components.